In a study of 78 patients in Sri Lanka, researchers found that 10 suffered severe weakness in their neck and limb muscles and five of these eventually developed respiratory failure.

Respiratory failure is the major cause of death after poisoning by organophosphates, a compound used in many insecticides and herbicides.

"In all 10 patients we demonstrated that the neuromuscular junction progressively fails, leading to muscle weakness," Pradeepa Jayawardane, a clinical pharmacology lecturer at the University of Sri Jayawardenepura in Sri Lanka, wrote in an email to Reuters.

The researchers applied electric shocks to certain muscles of the patients, using a technique called "repetitive nerve stimulation" (RNS).

Specific changes were seen in nerve transmissions in the 10 patients and five of them went on to develop respiratory failure.

"We believe that RNS is a predictor of respiratory failure and these findings would be useful once they are validated in future prospective studies," Jayawardane wrote.

"Those who are at risk of respiratory failure can be diagnosed early and directed to places where more facilities are available to manage them," he added.

About half the people in developing countries in Asia who kill themselves do it using pesticides, and aid agencies have been lobbying to ban or regulate their use.

Many studies have shown most people who commit suicide using pesticides act on impulse and their deaths could be prevented if lethal chemicals were not available. (Reporting by Tan Ee Lyn; Editing by Jerry Norton)